1. Field of the Invention
The invention concerns a drive system for a boat propeller including a motor that delivers a specific nominal motor torque, and including a reverse gearbox arranged between motor and propeller.
2. Prior Art
Such a drive system is known from U.S. Pat. No. 2,298,310. This prior drive system advantageously utilizes a purely hydrodynamic reverse gearbox wherein the travel direction can be reversed solely by switching the contact between two hydrodynamic working circuits. For instance, with the hydrodynamic coupling filled while travelling forward, all that needs to be done to reverse the travel direction is to fill the reverse converter and at the same time to empty the coupling. Thus, the reversing maneuver can be completed within a relatively short time without causing wear because mechanical shift elements are not needed for the reversing maneuver.
According to the aforementioned U.S. Pat. No. 2,298,310, another hydrodynamic torque converter is provided for forward travel, in addition to the hydrodynamic coupling. Drive systems for boat propellers are known as well from the U.S. Pat. No. 4,305,710 where the transfer of power from a forward direction occurs either through a multiple disk coupling or through a hydrodynamic torque converter to a reverse direction through a hydrodynamic torque converter. Mechanical couplings, such as multiple disk couplings, have the disadvantage of being associated with wear. During forward movement, it is undesirable for power transfer to occur through a hydrodynamic torque converter because of the relatively low efficiency of the converter.